Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
It is increasingly common for people to use client-side devices to communicate via a radio access network (RAN) with other devices, whether those devices are directly connected to the same RAN or to another network (such as another RAN or a transport network, as examples) to which that RAN directly or indirectly provides access. In a typical arrangement, a base station of a RAN may radiate to define a wireless coverage area in which mobile stations (such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices) can operate. In turn, each base station is typically coupled with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a mobile station operating within a coverage area of a base station can engage in air-interface communication with the base station and can thereby communicate via the base station with various remote network entities or with other mobile stations.
In practice, communications over the air-interface between a base station and a mobile station are structured in accordance with a particular air-interface protocol or “radio access technology,” with communications from the base station to mobile stations defining a “forward link” (or downlink) and communications from the mobile stations to the base station defining a “reverse link” (or uplink). Numerous such protocols are well known in the art, and others may be developed in the future. Examples of existing protocols include CDMA (e.g., 1×RTT, 1× Advanced, 1×EV-DO), LTE, WiMAX, iDEN, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, microwave, satellite, MMDS, Wi-Fi (e.g., IEEE 802.11), and Bluetooth. Each protocol may define its own procedures for initiation of calls, handoff between coverage areas, and functions related to air-interface communication.
Within the context of a RAN, the term “base station” is sometimes used to describe simply a device known as a base transceiver station (BTS), which contains the hardware, antennas, and so forth that actually conduct the over-the-air portion of the communication with the mobile station on behalf of the RAN. At times, however, the term “base station” is used to refer to a combination of (i) one or more BTSs and (ii) a device known as a base station controller (BSC) (or radio network controller (RNC)), which controls the BTS(s) and connects it (them) to the rest of the network. Further, a base station may encompass functions of one or more other RAN entities as well.
In a typical scenario, a mobile station registers with a RAN via a particular BTS, and then operates in what is known as “idle mode” on a carrier frequency in a coverage area provided by that BTS. If another telephone, computer, or other communication device attempts to contact the mobile station, the RAN will typically send the mobile station a page message via at least that particular BTS. The mobile station may respond by requesting and establishing communication on what is known as an air-interface traffic channel (or simply a traffic channel), and proceed to conduct the relevant communication. In other instances, the mobile station may itself originate a communication, in which case the mobile station sends the RAN an origination request in order to request and establish communication on a traffic channel to conduct the relevant communication. In either scenario, after the RAN has established a radio link and allocated a traffic channel for use by the mobile station, the mobile station is said to be operating in what is known as an active/connected mode.
If a mobile station loses communication with the network when the mobile station is engaged in a call in the active/connected mode, the mobile station may experience a call drop. This may happen, for example, if the mobile station is active/connected in a single coverage area and loses communication with the base station serving that coverage area, or if the mobile station is active/connected in multiple coverage areas at once and loses communication with the one or more base stations serving those coverage areas. In practice, when a mobile station experiences a call drop, the mobile station may responsively scan for coverage once again and a user of the mobile station may manually re-originate the call. Alternatively, some air-interface protocols include a call recovery feature that facilitates reconnecting communications automatically without manual intervention from a user when a mobile station experiences a call drop.